<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        div{
            height:100px;
            width:100px;
            background-color: aquamarine;
            position: absolute;
            top:0;
            bottom:0;
            left:0;
            right:0;
            margin:auto;

            /* position: absolute;
            top:0;
            bottom:0;
            margin:auto 0; */
            
            /* top:50%;
            transform: translateY(-50%); */
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>